Balancing Act...

Secrets, tips, tools, design considerations, materials, the "science" behind it all, and other topics related to building the cars and semi-trucks.
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tlz_allen
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Balancing Act...

Post by tlz_allen »

I know there is another discussion taking place about where weight should be distributed, but I need a little information on cars that we have for the Timothy Cup races operated by Raceway Ministries of California. The cars are all precut and come with the silhouette of a NASCAR stock car.

Last year I hollowed out the interior of my son's car and placed the weights in front of the rear axle, elevated near the roof of the car.

My questions are...

1 - Was this a good idea? (We got 6th out of 75 cars)

2 - Is there some formula for balancing a car and distributing the weight? My dad was an engineer and it seemed that he had a formula for everything on the planet. Does such a thing exist?!?!
Tim Allen
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Stan Pope
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Re: Balancing Act...

Post by Stan Pope »

tlz_allen wrote:Last year I hollowed out the interior of my son's car and placed the weights in front of the rear axle, elevated near the roof of the car.

My questions are...

1 - Was this a good idea? (We got 6th out of 75 cars)

2 - Is there some formula for balancing a car and distributing the weight? My dad was an engineer and it seemed that he had a formula for everything on the planet. Does such a thing exist?!?!
Two important issues...

1. mount the weight where a small bump that raises any wheel causes the least motion of the CM. This usually means to keep it low in the car.
2. keep enough weight on each wheel to keep that wheel from sliding sideways. for a three sheeler, this usually means at least one ounce on the front wheel ... more or less depending on alignment and track.
Stan
"If it's not for the boys, it's for the birds!"
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MERuhl
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Re: Balancing Act...

Post by MERuhl »

After reading up on the subject on various websites, then discussing it here with Stan and Randy, my son and I came up with a very easily-implemented - but still untried, as our race isn't until Nov. 7 - solution.

In our attempt to keep the weight as far back and low as possible (with "far back" taking precedence), we used a combination of the Pinecar.com round weights and tapered weights. We got these from our local hobby shop.

We drilled three 3/8"-diameter holes in the tail-end of the car, side-by-side, as low as we could and still leave some wood over the axles (which we re-cut to maximize the wheel-base length). We drilled the holes about 1.25" deep. We cut the round weights basically in half, so that we had a half-ounce weight in each hole. The weights fit perfectly in the holes, almost flush with the rear of the car.

We then took the flat, tapered weight and snapped off a few sections from each end, reducing its weight from 2 to 1 ounce. I carved out a rectangular section on the bottom of the car, deep enough to ensure that we'd have plenty of underbody clearance. We played around with the position of the underbody weight until we got the car to balance exactly 1.25" in front of the rear axle, per Stan's and Randy's advice.

With the wheels on, the car is a skosh over 5 ounces, with exactly 1 ounce of downward force on the front wheels (well, one of them anyway - we raised the front right wheel about 1/16").

We set up two cars this way. The race isn't for another two weeks. I'll post our results.
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MERuhl
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Re: Balancing Act...

Post by MERuhl »

I should point out that we're racing Awana Grand Prix cars, but it appears that this technique should work well regardless. Depending on the track type, you could easily adjust the weight distribution by using longer round weights and less belly weight, or vice versa. I was looking for a technique that my son will be able to execute as he gets older (he's 8, this is his second Grand Prix).
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Stan Pope
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Re: Balancing Act...

Post by Stan Pope »

MERuhl wrote:We set up two cars this way. The race isn't for another two weeks. I'll post our results.
Ser kewl! Now you have plenty of time to get the alignment "dead on." That's what you hear people who are not "in the know" talking about "luck." Oops! That is a different thread!
Stan
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MERuhl
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Re: Balancing Act...

Post by MERuhl »

"I'm a great believer in luck, and I find the harder I work the more I have of it."
Thomas Jefferson
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Stan Pope
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Re: Balancing Act...

Post by Stan Pope »

Jefferson had the advantage not only of working hard but also working smart! Both are necessary.
Stan
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Gavin Chafin
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Re: Balancing Act...

Post by Gavin Chafin »

"I'm a great believer in luck, and I find the harder I work the more I have of it."
Thomas Jefferson
Now, that's a great saying. I'll have to remember that one.
Jefferson had the advantage not only of working hard but also working smart! Both are necessary.
Can't agree more. Through personal experience, I’ve found that the “Working Smart” part is the more important of the two. Working smart can save you hours of unnecessary work.
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